1. Field of the Invention
The present invention relates to a chemically amplified resist composition, and more particularly, to a photosensitive polymer containing silicon and a resist composition comprising the same.
2. Description of the Related Art
As processes for manufacturing semiconductor devices become more complicated and the integration density of semiconductor devices increases, the need to form finer patterns becomes more pronounced. Furthermore, to manufacture semiconductor memory devices having a capacity of 1 Gigabit or more, a pattern size having a design rule of 0.2 xcexcm or less is needed. Accordingly, there is a limitation in forming such a fine pattern using conventional photoresist materials using a KrF excimer laser (248 nm). For this reason, a lithography technique using a new exposure light source, the ArF excimer laser (193 nm), has emerged.
However, a resist material suitable for use in lithography with the ArF excimer laser causes many problems for practical use, compared with conventional resist materials. The most serious problem is the collapse of patterns with respect to an increase in the aspect ratio. Therefore, patterns must be formed using resist layers having a thickness of 4000 angstroms or less. Other problems associated with the ArF resist include the transmittance of the polymer. The ArF resist has inferior transmittance as compared to the KrF resist. This is another reason why the thickness of the ArF resist layer must be reduced.
Almost all well-known ArF resists have a resistance to dry etching that is equal or inferior to that of the KrF resist. Therefore, when an underlying layer is patterned by lithography using resist patterns obtained from the conventional resist materials, a satisfactory profile cannot be obtained.
Recently, to solve the foregoing problems, a technique using a bi-layer resist (BLR) has been suggested. In a process using BLR, the lithography is performed using a resist material containing silicon. Silicon atoms within the resist material are glassed in the form of SiOX during dry etching by O2 plasma to form a cured layer, and the cured layer is used as an etching mask during a subsequent dry etching process. Therefore, when the aspect ratio is large, resistance to dry etching is increased by the curing layer, so that it is easy to form patterns, and collapse of patterns can also be prevented. As a result, patterns having a large aspect ratio can be formed with high resolving power.
The amount of silicon in a polymer is an important factor for a BLR. Generally, as the amount of silicon increases, the likelihood that there will be problems due to a reduction in the thermal stability of the resist layer and the wettability to a developer increases. Therefore, the polymer must contain the right amount of silicon for a BLR process, and development of a resist material having excellent thermal stability and wettability to a developer becomes a serious requirement.
It is a feature of the present invention to provide a photosensitive polymer that has a sufficient silicon content, that has a reduced manufacturing cost, and that provides excellent lithography characteristics when used as a resist material.
It is another feature of the present invention to provide a resist composition having a silicon content sufficient to be used as a BLR for ArF excimer laser lithography, and at the same time, has excellent thermal stability and wettability to a developer.
In accordance with one aspect of the present invention, there is provided a photosensitive polymer comprising a copolymer including acrylate or methacrylate monomer unit having a group indicated as the following formula (I), and a maleic anhydride monomer unit, 
wherein R1, R2, and R3 are independently a hydrogen atom, a C1-C4 alkyl group, a C1-C4 alkoxy group, a phenyl group, a benzyl group, a phenoxy group, or xe2x80x94M(Rxe2x80x2)3, wherein M is Si, Ge, Sn, or OSi, and each Rxe2x80x2 independently is a C1-C4 alkyl group, a C1-C4 alkoxy group, a phenyl group, or a phenoxy group.
In a more particular embodiment, the photosensitive polymer comprises a copolymer having the following structural formula (II): 
wherein R4 is a hydrogen atom or a C1-C4 alkyl group, R5, R6, and R7 are independently a hydrogen atom, a C1-C4 alkyl group, a C1-C4 alkoxy group, a phenyl group, a benzyl group, a phenoxy group, or xe2x80x94M(Rxe2x80x2)3, wherein M is Si, Ge, Sn or OSi, and each Rxe2x80x2 independently is a C1-C4 alkyl group, a C1-C4 alkoxy group, a phenyl group, or a phenoxy group, and m/(m+n) is between about 0.2-0.9.
In another more particular embodiment, the photosensitive polymer comprises a copolymer having the following structural formula (III): 
wherein R4 is a hydrogen atom or a C1-C4 alkyl group, R5, R6, R7, R8, and R9 are independently a hydrogen atom, a C1-C4 alkyl group, a C1-C4 alkoxy group, a phenyl group, a benzyl group, a phenoxy group, or xe2x80x94M(Rxe2x80x2)3, wherein M is Si, Ge, Sn or OSi, and each Rxe2x80x2 independently is a C1-C4 alkyl group, a C1-C4 alkoxy group, a phenyl group, or a phenoxy group, and m/(m+n) is between about 0.2-0.9.
In a further more particular embodiment, the photosensitive polymer comprises a copolymer having the following structural formula (IV): 
wherein R4 is a hydrogen atom or a C1-C4 alkyl group, R5, R6, R7, R8, R9, R10, and R11 are independently a hydrogen atom, a C1-C4 alkyl group, a C1-C4 alkoxy group, a phenyl group, a benzyl group, a phenoxy group, or xe2x80x94M(Rxe2x80x2)3, wherein M is Si, Ge, Sn or OSi, and each Rxe2x80x2 independently is a C1-C4 alkyl group, a C1-C4 alkoxy group, a phenyl group, or a phenoxy group, and m/(m+n) is between about 0.2-0.9.
In accordance with another aspect of the present invention, there is provided a photosensitive polymer comprising a terpolymer including an acrylate or methacrylate monomer unit having a group indicated as the following formula (I), a maleic anhydride monomer unit, and a cyclic vinyl ether monomer unit, 
wherein R1, R2, and R3 are independently a hydrogen atom, a C1-C4 alkyl group, a C1-C4 alkoxy group, a phenyl group, a benzyl group, a phenoxy group, or xe2x80x94M(Rxe2x80x2)3, wherein M is Si, Ge, Sn, or OSi, and each Rxe2x80x2 independently is a C1-C4 alkyl group, a C1-C4 alkoxy group, a phenyl group, or a phenoxy group.
In a more particular embodiment, the photosensitive polymer comprises a terpolymer having the following structural formula (V): 
wherein, R4 is a hydrogen atom or a C1-C4 alkyl group, R5, R6, and R7 are independently a hydrogen atom, a C1-C4 alkyl group, a C1-C4 alkoxy group, a phenyl group, a benzyl group, a phenoxy group, or xe2x80x94M(Rxe2x80x2)3, wherein M is Si, Ge, Sn, or OSi, and each Rxe2x80x2 independently is a C1-C4 alkyl group, a C1-C4 alkoxy group, a phenyl group, or a phenoxy group, k is an integer from 1 to 6, and m/(m+n) is between about 0.2-0.9.
In another more particular embodiment, the photosensitive polymer comprises a terpolymer having the following structural formula (VI): 
wherein R4 is a hydrogen atom or a C1-C4 alkyl group, R5, R6, R7, R8, and R9 are independently a hydrogen atom, a C1-C4 alkyl group, a C1-C4 alkoxy group, a phenyl group, a benzyl group, a phenoxy group, or xe2x80x94M(Rxe2x80x2)3, wherein M is Si, Ge, Sn, or OSi, and each Rxe2x80x2 independently is a C1-C4 alkyl group, a C1-C4 alkoxy group, a phenyl group, or a phenoxy group, k is an integer from 1 to 6, and m/(m+n) is between about 0.2-0.9.
In a further more particular embodiment, the photosensitive polymer comprises a terpolymer having the following structural formula (VII): 
wherein R4 is a hydrogen atom or a C1-C4 alkyl group, R5, R6, R7, R8, R9, R10, and R11 are independently a hydrogen atom, a C1-C4 alkyl group, a C1-C4 alkoxy group, a phenyl group, a benzyl group, a phenoxy group, or xe2x80x94M(Rxe2x80x2)3, wherein M is Si, Ge, Sn or OSi, and each Rxe2x80x2 independently is a C1-C4 alkyl group, a C1-C4 alkoxy group, a phenyl group, or a phenoxy group, k is an integer from 1 to 6, and m/(m+n) is between about 0.2-0.9.
In accordance with an additional aspect of the present invention, there is provided a resist composition comprising (a) a photosensitive polymer and (b) a photoacid generator (PAG). The photosensitive polymer comprises a copolymer of (a-1) an acrylate or methacrylate monomer having a group indicated by the formula (I) and (a-2) a comonomer selected from the group consisting of a maleic anhydride monomer and a cyclic vinyl ether monomer, 
wherein R1, R2, and R3 are independently a hydrogen atom, a C1-C4 alkyl group, a C1-C4 alkoxy group, a phenyl group, a benzyl group, a phenoxy group, or xe2x80x94M(Rxe2x80x2)3, wherein M is Si, Ge, Sn, or OSi, and each Rxe2x80x2 independently is a C1-C4 alkyl group, a C1-C4 alkoxy group, a phenyl group, or a phenoxy group.
Particular embodiments of the photosensitive polymer comprised in a resist composition according to the present invention include photosensitive polymers of formulas (II)-(VII) as described above.
Korean Patent Application No. 00-75944, filed on Dec. 13, 2000, and entitled: xe2x80x9cPhotosensitive Polymer Containing Silicon and Resist Composition Comprising the Same,xe2x80x9d is incorporated by reference herein in its entirety.
In particular embodiments of the resist composition according to the present invention, the weight average molecular weight of the photosensitive polymer is from about 3,000 to about 100,000.
Also, specific embodiments of the resist composition according to the present invention include the photoacid generator (PAG) in an amount from about 1 to about 30 wt % based on the weight of the photosensitive polymer. Preferably, the PAG is selected from the group consisting of triarylsulfonium salts, diaryliodonium salts, sulfonates, and mixtures thereof. More preferably, the PAG is triphenylsulfonium triflate, triphenylsulfonium antimonate, diphenyliodonium triflate, diphenyliodonium antimonate, methoxydiphenyliodonium triflate, di-t-butyldiphenyliodonium triflate, 2,6-dinitrobenzyl sulfonates, pyrogallol tris(alkylsulfonates), N-hydroxysuccinimide triflate, norbornene dicarboximide triflate, triphenylsulfonium nonaflate, diphenyliodonium nonaflate, methoxydiphenyliodonium nonaflate, di-t-butyldiphenyliodonium nonaflate, N-hydroxysuccinimide nonaflate, norbornene dicarboximide nonaflate, triphenylsulfonium perfluorobutanesulfonate, triphenylsulfonium perfluorooctanesulfonate (PFOS), triphenylsulfonium perfluorocamphorsulfonate, diphenyliodonium PFOS, methoxydiphenyliodonium PFOS, di-t-butyldiphenyliodonium triflate, N-hydroxysuccinimide PFOS, norbornene dicarboximide PFOS, or a mixture thereof.
The resist composition according to the present invention may further include an organic base. The organic base preferably is contained in an amount of about 0.01 to about 2.0 wt % based on the weight of the photosensitive polymer. Preferably, the organic base is a compound composed of a tertiary amine compound or a mixture of at least two tertiary amine compounds. More preferably, the organic base is triethylamine, triisobutylamine, triisooctylamine, triisodecylamine, diethanolamine, triethanolamine, or a mixture thereof.
More particular embodiments of the resist composition according to the present invention can further include a surfactant in an amount from about 30 to about 200 ppm.
Also, particular embodiments of the resist composition according to the present invention can further include a dissolution inhibitor in an amount from about 0.1 to about 50 wt % based on the weight of the photosensitive polymer.
The photosensitive polymer according to the present invention contains an element such as Si, Ge or Sn in its protecting group, and a maleic anhydride monomer or a cyclic vinyl ether monomer occupying a relatively small part within the polymer as an adhesion promoter. Therefore, the photosensitive polymer according to the present invention can be manufactured at low cost, and the resist composition can provide sufficient resistance to dry etching, and secure excellent thermal stability and wettability to a developing solution.
The present invention is further illustrated by the following non-limiting examples.